Centripetal Force

To investigate the relationship between the centripetal force action on an object moving in a circle of constant radius and the frequency of revolution.

Hypothesis:

The centripetal force of an object of mass (m) moving at a constant velocity (v) and radius (r) is given by ΣF = = 4π2rmf2. where:

Fc is the centripetal force in N

Fg is the force of gravity in N

r is the radius of the string in m

ms is the mass of the rubber stopper in kg

ml is the mass of the suspended load in kg

g is the gravitation in m s-2

From that equation, I can deduce that if the frequency of object spinning is increased, the centripetal force will increase. Also, in this experiment, the force of gravity acting on the suspended mass should be the one providing the centripetal force. This force is given by: where in this case m is the mass of the suspended load and g is the gravity.

Variables:

Dependent

Independent

Controlled

The period of the revolution measured by using stopwatch, the frequency and the centripetal force

load mass (varied from 10 gr until 50 gr with interval 10 gr each)

The small of soft mass (rubber stopper)

horizontal string length

Apparatus:

Name

Quantity

Accuracy

Thin plastic tube about 15 cm long, with no sharp edges

1

±0.5cm

1.5 of fishing line

1

-

Paper clip

1

-

Small soft mass (rubber stopper)

1

-

Mass carrier and slotted masses (10 g each)

As needed

-

Stop watch

1

∆t ±0.005s

Metre ruler

1

∆l ± 0.5 cm

Electronic Scale

1

∆m ± 0.005 g

Method:

Securely tie one end of the fishing line to a small, soft mass.

(Since this is going to be twirled around your head, make sure the mass isn’t too hard!).

Pass the line down through a thin plastic tube and attach a 10 g slotted mass carrier to the end as shown in the diagram. Attach a paper clip to the line to act as a marker for a measured radius of around 1 metre.

Add 10 g masses to the mass carrier to make a total mass of 20 g.

Twirl the stopper in a horizontal circular path at a speed that pulls the paper clip up to, but not touching, the bottom of the tube.

Get a partner to keep an eye on the position of the clip to ensure that the speed of rotation stays quite constant. Practise doing so for a while before trying any measurements.

Maintain the speed of revolution and measure the time taken for 10 revolutions of the small mass.

Add an extra 10 g to the mass carrier and repeat steps 2 and 3.

Add another 10 g to the mass carrier and repeat steps 2 and 3. Keep adding an extra 10 g mass to the mass carrier.

There will be some improvements in this experiment that I need if I’ll do this experiment again. First of all we need to practice to swing it horizontally, and when we want to record the revolution after 10 swings, we must carefully count the revolution because sometimes our eyes can’t follow the revolution. Secondly, we also need more careful when swing because sometimes the mass can contact our head or our friends. I also need to keep the string is not moving so that the length can be measured perfectly. To get more accurate results, we can also give an alternative independent variable such as the length of the string. By getting the results from the different mass and different length of string it will make the data more accurate to prove the theory and hypothesis.

Related International Baccalaureate Physics essays

Even though the data are not very accurate and prise, there are ways to improve it, which would be discussed in the next section. A few of variables are controlled during the course of the experiment to make this a fair test.

Evaluation (Sources/Solutions of error) This section deals with the sources of error, and the improvements that one can utilise to improve this experiment. The first two major sources of error are quite evident. The major source of error as described in previous sections is the fact that the length of

Whilst with my right hand I got ready to press the 'start' button of the digital timer. I then released the metal bar without exerting any other force and this caused to oscillate back and forth from the 90 degrees position to its original or resting position and back again.

inverse of the square root of mass and graphing it against the time, it can be seen that the non-linear relationship becomes linear. This further proves that there is a proportional relationship between the inverse of the square rot of mass and the time, or in other words, an inverse

Determine the spring constant k of the spring used. Attach a mass m to the spring on the ring stand and measure the displacement x of the spring relative to its equilibrium position. The value where will give you the spring constant k in .

Five trials for data point two were then conducted and recorded in the same fashion using the 50g mass. We then conducted five more trials for data point three, using the 100g mass (actual mass was 100.2) in the same manner, and recorded the data.

and the time taken for that as our example. = 0.090 + 0.21 = > 0.300 After we have done this (?Equipment + ?Reaction + ?Average uncertainty) we divide it by 10 in order to obtain ?Period. = 0.300 / 10 = 0.030 Therefore, ? Period for the first mass (0.100 kg)